U.S. patent application number 10/552900 was filed with the patent office on 2006-11-23 for transponder reader capable of reading transponders having different signaling protocols.
Invention is credited to Bjorn Carlson, Inga-Lill Solberg.
Application Number | 20060261928 10/552900 |
Document ID | / |
Family ID | 20291022 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060261928 |
Kind Code |
A1 |
Solberg; Inga-Lill ; et
al. |
November 23, 2006 |
Transponder reader capable of reading transponders having different
signaling protocols
Abstract
The present invention provides an apparatus and method that can
in a simple and cost-effective way read transponders from different
systems implementing different communication protocols. The
transponder reader comprises an antenna means for sending a first
analogue signal to one of said transponders and receiving a second
analogue signal from said transponder, said transponder reader
further comprises means for analysing, e.g. demodulating,
detecting, decode said signal received by said antenna means
according to at least two different protocols.
Inventors: |
Solberg; Inga-Lill;
(Huddinge, SE) ; Carlson; Bjorn; (Tumba,
SE) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 8910
RESTON
VA
20195
US
|
Family ID: |
20291022 |
Appl. No.: |
10/552900 |
Filed: |
April 7, 2004 |
PCT Filed: |
April 7, 2004 |
PCT NO: |
PCT/SE04/00550 |
371 Date: |
June 28, 2006 |
Current U.S.
Class: |
340/10.4 ;
340/10.1; 340/572.4 |
Current CPC
Class: |
H04L 69/18 20130101;
H04L 29/06 20130101 |
Class at
Publication: |
340/010.4 ;
340/010.1; 340/572.4 |
International
Class: |
H04Q 5/22 20060101
H04Q005/22 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 14, 2003 |
SE |
0301096-4 |
Claims
1. A transponder reader arranged to read data from transponders,
wherein each of said transponders send data according to one
transponder signalling protocols, said transponder signalling
protocol is selected from a number of different transponder
signalling protocols, and a first and a second transponder signals
according to the same or different protocols, said transponder
reader comprises an antenna means for sending a first analogue
signal to one of said transponders and receiving a second analogue
signal from said transponders, and said transponder reader further
comprises means for analysing said signal received by said antenna
means wherein said transponder reader comprises a digital
processing means, said transponder reader comprises an analogue to
digital converter arranged to receive said second analogue signal
from said second analogue signal to supply said first digital
processing means, said digital processing means comprises analysing
means arranged to analyse said received digital signals according
to at least two different transponder signalling protocols.
2. The transponder reader according to claim 1, wherein said
analysing means comprises first demodulating, detecting and
decoding means for demodulating, detecting and decoding digital
signals according to a first transponder signalling protocol and
second demodulating, detecting and decoding means for demodulating,
detecting and decoding digital signals according to a second
transponder signalling protocol
3. The transponder reader according to claim 1, wherein said
transponder reader further comprises transmitting means for sending
said analysed first digital signal to post-processing means.
4. The transponder reader according to claim 1, wherein said
antenna means comprises means for controlling the antenna
characteristics, said antenna means comprises a digital interface
for receiving digital messages from said digital processing means
and transmitting digital messages to said digital processing means,
said antenna means controls said antenna characteristics in
dependence of said received digital messages, and said antenna
means transmit digital messages relating to the antenna
characteristics to said digital processing means.
5. The transponder reader according to claim 4, wherein said
digital messages comprises information selected from the group of
information comprising: antenna ready to send, antenna on line,
output amplification, and frequency tuning coefficients.
6. The transponder reader according to claim 1, wherein each of
said at least two protocols are selected from the group of
protocols including: half-duplex protocols, full-duplex protocols,
proprietor protocols (B-protocol) and read/write protocols.
7. The transponder reader according to claim 1, wherein said
digital processing means supply second digital signals to a digital
to analogue converter for converting said digital signal to said
first analogue signal, said digital to analogue converter supplies
said first analogue signal to said antenna means for
transmission.
8. The transponder reader according to claim 1, wherein said
digital processing means comprises means for demodulating said
first digital signal according to a first and at least a second
demodulation scheme.
9. The transponder reader according to claim 8, wherein said
digital processing means comprises means for detection of symbols
from said demodulated digital signal cording to a first and at
least a second symbol detection scheme.
10. The transponder reader according to claim 9, wherein said
digital processing means comprises means for decoding symbols from
said detected symbols according to a first and at least a second
symbol decoding scheme.
11. The transponder reader according to claim 10, wherein said
decoding comprises or consists of performing an error detection
check e.g. a cyclic redundancy check.
12. The transponder reader according to claim 10, wherein said
transponder reader comprises means for detecting which of said
first and at least second means for demodulating, detection, and
decoding that produces the best signal detection quality and using
said means.
13. The transponder reader according to claim 10, wherein an
operator selects which demodulator, detector and decoder to be used
by said digital processing means.
14. The transponder reader according to claim 1, wherein said one
of at least two different transponder signalling protocols is a
full duplex protocol, and said first analogue signal is subtracted
from said second analogue signal to remove the contribution from
the first analogue signal from the reception of said second
analogue signal.
15. The transponder reader according to claim 14, wherein said
first analogue signal is boosted before being subtracted from said
second analogue signal.
16. The transponder reader according to claim 1, wherein said
transponder reader comprises means for deciding which of at least
said two different transponder signalling protocols that said
transponder is using in responding to said first analogue signal,
and using said protocol.
17. The transponder reader according to claim 16, wherein said
decision is performed in a start up sequence and that said
transponder reader assumes that all transponders are working
according to said detected protocol.
18. The transponder reader according to claim 1, wherein an
operator selects the appropriate transponder signalling
protocol.
19. The transponder reader according to claim 4, wherein said
transponder reader comprises means for setting antenna
characteristics in dependence of detected environmental
characteristics so as to achieve optimal signalling detection
quality relation to the electromagnetic environment.
20. The transponder reader according to claim 9, wherein the phase
of said first analogue signal is controlled.
21. A method for reading data from transponders, wherein each of
said transponders send data according to one transponder signalling
protocols, said transponder signalling protocol is selected from a
number of different transponder signalling protocols, and--a first
and a second transponder signals according to the same or different
protocols, comprising sending a first analogue signal to one of
said transponders and receiving a second analogue signal from said
transponders using an antenna means, and analysing said second
analogue signal received by said antenna means, wherein converting
said second analogue signal from the analogue domain to a first
digital signal in the digital domain, supplying said first digital
signal to digital processing means, analysing said received first
digital signal using said digital processing means for establishing
which of at least two different transponder signalling protocols
said transponder uses, selecting said established one of said at
least two different transponder signalling protocols, and analysing
said first digital signal according to said selected transponder
signalling protocol.
22. The method according to claim 21, wherein said analysing
comprises demodulating, detecting and decoding digital signals
according to a first and at least a second transponder signalling
protocol.
23. The method according to claim 21, further comprising the step
of sending said analysed first digital signal to post-processing
means.
24. The method according to claim 21, wherein said antenna means
comprises means for controlling the antenna characteristics, said
antenna means comprises a digital interface for receiving digital
messages from said digital processing means and transmitting
digital messages to said digital processing means, and
characterised by the further steps of controlling said antenna
characteristics in dependence of said received digital messages,
and transmitting digital messages from said antenna means relating
to the antenna characteristics to said digital processing
means.
25. The method according to claim 24, wherein said digital messages
comprises information selected from the group of information
comprising: antenna ready to send, antenna on line, output
amplification, and frequency tuning coefficients.
26. The method according to claim 21, wherein each of said at least
two protocols are selected from the group of protocols including:
half-duplex protocols, full-duplex protocols, proprietor protocols
(B-protocol), and read/write protocols.
27. The method according to any of claims 21-26 claim 21, wherein
supplying second digital signals, from said digital processing
means to a digital to analogue converter for converting said
digital signal to said first analogue signal, supplying said first
analogue signal, from said digital to analogue converter to said
antenna means for transmission.
28. The method according to claim 21, wherein said digital
processing means comprises means for demodulating said first
digital signal according to a first and at least a second
demodulation scheme.
29. The method according to claim 28, wherein said digital
processing means comprises means for detection of symbols from said
demodulated digital signal according to a first and at least a
second symbol detection scheme.
30. The method according to claim 29, wherein said digital
processing means comprises means for decoding symbols from said
detected symbols according to a first and at least a second symbol
decoding scheme.
31. The method according to claim 30, wherein said decoding
comprises or consists of performing a error detection check e.g. a
cyclic redundancy check.
32. The method according to claim 30, comprising the steps of:
detecting which of said first and at least second means for
demodulating, detection, and decoding that produces the best signal
detection quality and using said means.
33. The method according to claim 30, wherein an operator selects
which demodulator, detector and decoder to be used by said digital
processing means.
34. The method according to claim 21, wherein said one of at least
two different transponder signalling protocols is a full duplex
protocol, and wherein the method further includes the steps of:
subtracting said first analogue signal from said second analogue
signal to remove the contribution from the first analogue signal
from the reception of said second analogue signal.
35. The method according to claim 34, comprising the step of:
boosting said first analogue signal before subtracting said first
analogue signal from said second analogue signal.
36. The method according to claim 21, comprising the step of:
deciding which of at least said two different transponder
signalling protocols that said transponder is using in responding
to said first analogue signal and using said protocol.
37. The method according to claim 36, comprising the step of:
performing said decision in a start up sequence and assuming that
all transponders are working according to said detected
protocol.
38. The method according to claim 21, wherein an operator selects
the appropriate transponder signalling protocol.
39. The method according to claim 24, comprising the step of:
setting antenna characteristics in dependence of detected
environmental characteristics so as to achieve optimal signalling
detection quality in relation to the electromagnetic
environment.
40. The method according to claim 24, wherein controlling the phase
of said first analogue signal.
Description
TECHNICAL FIELD
[0001] The present invention relates to a transponder reader and a
method therefore. More specifically the present invention relates
to a transponder reader capable of reading transponders having
different signalling protocols.
BACKGROUND OF THE INVENTION
[0002] Transponders were originally electronic circuits that were
attached to some item whose position or presence was to be
determined. The transponder functioned by replying to an
interrogation request received from an interrogator, or transponder
reader, either by returning some data from the transponder such as
an identity code or the value of a measurement, or returning the
original properties of the signal received from the interrogator
with virtually zero time delay, thereby allowing ranging
measurements based on time of flight. As the interrogation signal
is generally very powerful, and the returned signal is relatively
weak, the returned signal would be swamped in the presence of the
interrogation signal.
[0003] The functioning of the transponder was therefore to move
some properties of the returned signal from that of the
interrogation signal so that both could be detected simultaneously
without the one swamping the other. The most common property to
change is the transmission frequency meaning that the transponder
might receive the interrogation frequency at one frequency, and
respond on another frequency that is separated sufficiently with
regard to frequency so that both may be detected
simultaneously.
[0004] Transponder systems have recently started to become major
players in the field of electronic identification. Within this
application, it is necessary to make the transponders as cheap as
possible, and rather to build the sophistication into the readers.
This lack of sophistication generally means that changing the
transmission frequency is no longer an option, as the frequency
translation needs expensive and complex tuned circuitry. Instead
the transponders have given up the ranging ability and rather time
slice the communications channel with the interrogator. Here the
interrogator (called a reader) sends an interrogation signal for a
limited time. The transponder receives the signal and waits for its
completion, and then responds on the same frequency with its
identity and data code.
[0005] The devices are sometimes called transponders and are also
sometimes called tags, because their end application eventually
will be the tagging of goods or animals.
[0006] RFID stands for radio frequency identification. It is a
widely varied collection of technologies for various applications,
ranging from the high-speed reading of railway containers to
applications in retail that can be regarded as a potential
successor to the bar-coding technologies in use today to
identification of animals in farms. RFID is based around radio or
electromagnetic propagation. This has the ability to allow energy
to penetrate certain goods and read a tag that is not visible
thereby to identify those goods remotely, either in the form of an
identity code or more simply that something is present (EAS).
Different frequencies of the radio system result in different
reading ranges and properties of the system.
[0007] Commonly available tags have an operating frequency in the
range from 60 kHz to 5.8 GHz depending on application. In operation
one can generally say that there are three different types of
technologies being implemented. They are: [0008] Magnetic based
RFID technologies [0009] EAS based technologies [0010] Electric
field based RFID technologies
[0011] Electric field coupled transponders generally provide vastly
increased ranges over their magnetic counterparts. Rather than
being limited to the ranges of the lines of force emitting from a
magnetic field generator, they use the electric field propagation
properties of radio communication to convey energy and data from
the reader to the transponder and data from the transponder to the
reader.
[0012] Electric field propagation requires antenna systems that are
typically half a wavelength of the operating frequency in size.
(150 cm at 100 MHz, 15 cm at 1 GHz, 5 cm at 2.5 Ghz and 2.5 cm at
5.8 Ghz). This causes practical limits to how low a frequency to
start using E-field propagation methods due to the size of the
antenna.
[0013] Higher operating frequencies require more expensive
components and loose the ability to transfer energy at a rate of
the inverse of the wavelength squared.
[0014] In addition, the energy density of a signal radiated using
electric field coupling, decreases as the inverse of the distance
squared between the source and the transponder. Whereas sensitive
receivers can compensate for this loss of energy for the data
communications over long distances, passive transponders which use
the reader's energising field as a source of power are practically
limited to maybe ten meters (say at 400 MHz). Beyond that distance
(which reduces drastically with increased frequency to less than 1
meter at 2.5 GHz) it is necessary for the tags to use an external
battery as a source of power.
[0015] Electric field tags are available in many different
configurations and price ranges, particularly dependant on the
complexity of the transponder. If the transponder is a read/write
transponder and is required to operate beyond the range of passive
transponders, the receiver circuitry onboard can be expensive and
difficult to construct particularly if frequency stability is
needed with temperature.
[0016] However the invention of the backscatter modulation
principle at Lawrence Livermore Laboratories in the 1960s and the
skills of semiconductor designers to shrink all features into cheap
integrated circuits, has meant that electric field type tags in a
read only mode can be made extremely cheaply, most probably for
less than 10 US cents in high volume. Such a tag would be passive,
have no onboard tuned circuits, be read only, consist of a single
integrated circuit and a simple antenna, would operate at any of a
range of frequencies, be temperature insensitive, and would
broadcast a large data value when illuminated by a reader's
energising field. In such a system the reader is complex because it
provides the frequency stability, the energy of the system, and the
receiver selectivity to receive the weak return communications, but
the tags are very cheap. This is ideal for the situations where
there is one reader and many tags, such in large herds of farm
animals.
[0017] Electric field tags need to operate in an ordered spectrum
management system as their radiated energy (particularly from the
reader) can be detected by other sensitive receivers far away and
cause possible interference.
[0018] Recent developments in passive tag technology see the amount
of power needed to power up the tag dropping dramatically. The
reader radiates energy from its transmit antenna, some of which is
collected by the tag in an area around its antenna called the
"antenna's aperture". The size of this area is dependant upon the
characteristics of the tag antenna and the operating frequency of
the system, (e.g. a 915 MHz dipole has a 134 cm.sup.2 aperture).
Traditionally a 5 volt logic circuit in a transponder would need 55
milliwatts of RF energy to operate while recent developments see
this amount of power dropping to less than 1 milliwatt, thereby
dramatically reducing the power needed by the reader and increasing
the range over which passive transponders can operate
effectively.
[0019] A separate category also exists of "active" tags (battery
powered). These tags are "beacon" tags, that is they are not
interrogated by a reader, but wake themselves up from a low power
"sleep mode" periodically and broadcast their identity before
returning to "sleep mode". By broadcasting on a fixed frequency, a
sensitive receiver tuned to that frequency and within close
proximity to the tag will receive the identity message. This type
of transponder offers ranges up to hundreds of meters, but is not
suited for situations where the location of a tag is being
determined to a couple of meters range, or where very many tags are
present in the reader zone. Encryption technology has also been
added to these systems to stop unwanted tags being accepted as
valid codes by the reader.
[0020] Despite the hurdles, the greater range, higher data rates
and new technologies make these transponders suitable for a great
number of applications.
[0021] As can be understood from the description of prior art above
a number of different transponder systems or schemes are present
and more are continuously developed. Most of these systems continue
to push intelligence towards the reader to be able to produce
simple and cheap transponders or tags. It would thus be beneficial
if a reader could be designed to handle transponders from several
different systems without expensive hardware modification and
preferably in a dynamic manner.
SUMMARY OF THE INVENTION
[0022] It is a main object of the present invention to provide such
apparatus and method that at least alleviate the above
problems.
[0023] It is in this respect a particular object of the invention
to provide such an apparatus and method that can in a simple and
cost-effective way read transponders from different systems
implementing different communication protocols.
[0024] It is still a further object of the invention to provide
such apparatus and method that can read transponders from different
systems implementing different communication protocols in a dynamic
manner.
[0025] These objects among others are, according to a first aspect
of the present invention, attained by a transponder reader arranged
to read data from transponders, wherein said transponders send data
according to one transponder signalling protocol. The transponder
signalling protocol may be selected from a number of different
transponder signalling protocols.
[0026] Since the reader is designed to recognise transponders or
tags from different systems, one reader may handle herds of animals
wherein different animals wear tags from different transponder
systems.
[0027] The transponder reader comprises an antenna means for
sending a first analogue signal to one of said transponders and
receiving a second analogue signal from said transponder, said
transponder reader further comprises means for analysing, e.g.
demodulating, detecting, decode and transmitting said signal
received by said antenna means to post-processing means.
[0028] The first analogue signal is the signal to energise a
passive transponder, or to activate a semi-passive transponder. The
first analogue signal is occasionally denoted activation signal.
The first analogue signal may be continuous or intermittent for
full-duplex and half-duplex systems, respectively. The second
analogue signal is the signal sent from the transponder containing
identification information to be deduced by the reader using
demodulation, detection and decoding, to be described later. The
reader may then send the information to post-processing means such
as a database for storing the information.
[0029] The transponder reader comprises a digital processing means,
an analogue to digital converter arranged to receive said second
analogue signal from said antenna means, convert said second
analogue signal to a first digital signal and supply said first
digital signal to said digital processing means. The digital
processing means comprises analysing means e.g. demodulating,
detecting and decoding means arranged to demodulate, detect and
decode digital signals received according to at least two different
transponder signalling protocols, and the digital processing means
receives, demodulates, detects and decodes said first digital
signal and then transmits said decoded signal to said
post-processing means.
[0030] By transforming the received signal to the digital domain,
digital processing means can be utilised to process the digital
signal by any appropriate method, that is, according to one
selected protocol from a multitude of protocols.
[0031] These objects among others are, according to a second aspect
of the present invention, attained by a method for reading read
data from transponders, wherein each of said transponder send data
according to one transponder signalling protocols, the transponder
signalling protocol may be selected from a number of different
transponder signalling protocols.
[0032] The method comprises sending a first analogue signal to one
of said transponders and receiving a second analogue signal from
said transponders using an antenna means, demodulating, detecting,
and decoding said signal received by said antenna means and sending
said signal to post-processing means.
[0033] The method is further characterised in the steps of
converting said second analogue signal from the analogue domain to
a first digital signal in the digital domain and supplying said
first digital signal to digital processing means, wherein said
digital processing means comprises demodulating, detecting and
decoding means arranged to demodulate, detect and decode digital
signals received according to at least two different transponder
signalling protocols. The method continues to demodulate, detect
and decode said first digital signal according to a selected
transponder system and transmit said decoded signal to said
post-processing means.
[0034] According to a preferred embodiment the antenna means
comprises means for controlling the antenna characteristics and a
digital interface for receiving and transmitting digital messages
from said digital processing means. The antenna means controls said
antenna characteristics in dependence of said received digital
messages, and/or transmits digital messages relating to the antenna
characteristics to said digital processing means.
[0035] By this arrangement the antenna characteristics may be
controlled and adjusted to the circumstances prevailing. For
instance may the amplification be tuned in dependence of the
specific transponders used or the expected distance from the reader
for the specific application of the transponder reader.
[0036] In the application for identifying lactating animals in a
milking stall it is common that more than one transponder reader
are positioned in relatively close proximity. In these cases the
readers may disturb each other in a number of different ways. The
antenna characteristics may then be controlled and adjusted to
minimize the disturbances from the second reader during reading of
the transponder as well as to disturb the second reader to a
minimal extend when energizing transponders. By controlling the
phase of the activation signal for each transponder reader so that
they are coherent, minimal interference will occur between the
transponder readers.
[0037] For instance may the transponder reader set antenna
characteristics in dependence of detected environmental
characteristics so as to achieve optimal signalling detection
quality in relation to the electromagnetic environment.
[0038] According to one embodiment of the invention the protocols
can be half-duplex protocols, full-duplex protocols or proprietor
protocols. By designing a transponder reader according to the
invention it is possible to have one single reader, which may be
used for different protocols.
[0039] According to one embodiment of the transponder reader
according to the invention the digital processing means supply
second digital signals to a digital-to-analogue converter for
converting said second digital signal to said first analogue
signal, and the digital-to-analogue converter supplies said first
analogue signal to the antenna means for transmission. Thus the
digital processing means may control the characteristics of the
energising signal sent from the antenna for energizing transponder.
This may for instance be utilised for sending control signals to
transponders or simply to change the frequency of the energising
signal (activation signal).
[0040] According to yet a further embodiment of the invention the
digital processing means comprises means for demodulating a signal
according to several different methods. These may be implemented as
different blocks or may be different parts of the same block in the
digital processing means. The digital processing means may select
which demodulating method to be used in different ways. In one
embodiment the selection is made automatically and dynamically so
that the digital processing means selects the method, which is best
according to a specific criteria. According to another embodiment
an operator selects which method to use.
[0041] According to yet a further embodiment of the invention the
digital processing means comprises means for detection of symbols
from said demodulated digital signal and means for decoding symbols
from said detected symbols according to several schemes. These may
be implemented as different blocks or may be different parts of the
same block in the digital processing means.
[0042] Since the digital processing means comprises several
different demodulation, detection and decoding means the
transponder reader is very flexible and is able to read different
transponders.
[0043] The transponder reader may select the demodulating,
detection, and decoding means that produces the best signal
detection quality. Decoding may be simple CRC.
[0044] According to another embodiment of the invention, where a
full-duplex protocol is used the transponder reader may comprise
means for subtracting the first analogue signal from the second
analogue signal to remove the contribution from the first analogue
signal, transmitted by the antenna from the reception of said
second analogue signal received by the antenna. The first analogue
signal may be boosted and/or delayed before subtraction. By this
arrangement a more prominent response signal can be received from
the transponder since in full-duplex systems the energizing signal,
i.e. the first analogue signal, is transmitted continuously, i.e.
even at the reception of the signal from the transponder. Since the
first analogue signal is stronger, i.e. has higher amplitude, than
the second signal, the second signal may drown if the first signal
is not subtracted.
[0045] According to one embodiment of the invention the transponder
reader comprises means for deciding which transponder signalling
protocols that said transponder is using. This may be performed in
different ways. For instance may the transponder reader read a
first transponder in a start up sequence and that said transponder
reader then assumes that all subsequentially read transponders are
working according to said detected protocol or an operator may
select the appropriate transponder signalling protocol. As an
alternative the transponder reader may decide dynamically, for each
transponder, which protocol to be used. This decision may be based
on, for instance the detection rate or signal-to-noise ratio.
[0046] Further characteristics of the invention and advantages
thereof will be evident from the following detailed description of
embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] The present invention will become more fully understood from
the detailed description of embodiments of the present invention
given herein below and the accompanying FIGS. 1 to 10, which are
given by way of illustration only, and thus are not limitative of
the present invention.
[0048] FIG. 1 shows a schematic side view of a transponder reader
system according to the present invention.
[0049] FIG. 2 shows a block diagram of a preferred embodiment
according to the present invention.
[0050] FIG. 3 shows a block diagram of the interface between the
antenna means and the processing means in greater detail.
[0051] FIG. 4 shows a block diagram of the interface between the
antenna means and the processing means in greater detail.
[0052] FIG. 5 shows a block diagram of the processing means
according to a preferred embodiment of the invention in greater
detail.
[0053] FIGS. 6 and 7 show block diagrams for detecting implemented
in the processing means according to the invention.
[0054] FIGS. 8 and 9 show two different telegram layouts.
[0055] FIG. 10 shows a block diagram of the interface between the
processing means and the antenna means according to another
preferred embodiment of the invention.
PREFERRED EMBODIMENTS
[0056] In the following description, for purposes of explanation
and not limitation, specific details are set forth, such as
particular techniques and applications in order to provide a
thorough understanding of the present invention. However, it will
be apparent to one skilled in the art that the present invention
may be practiced in other embodiments that depart from these
specific details. In other instances, detailed descriptions of
well-known methods and apparatuses are omitted so as not to obscure
the description of the present invention with unnecessary
details.
[0057] FIG. 1 shows a schematic side view of an arrangement
according to the present invention. A transponder reader 101 is
connected to processing means 102, which in turn is connected to
post-processing means 103. In the application of registration of
lactating animals the post-processing means may for instance
include a database for registration of data relating to each
identified animal. The purpose of the transponder reader 101 and
the processing means 102 are to identify an animal passing through
the reader 101 in the direction indicated by the arrow 104. The
animals may for instance be on their way to a milking station,
where further data may be registered and conveyed to the
post-processing means 103 for storage in the database (not
shown).
[0058] FIG. 2 shows a schematic block diagram of an embodiment
according to the present invention. An antenna module 201 comprises
the actual antenna as well as analogue, and in one embodiment,
digital circuitry. The antenna module comprises means for adjusting
the antenna characteristics, such as matching circuits, means for
connecting or disconnecting parasitic elements, as well as
regulating the output power or the signal form and radiation
pattern. This is used for adapting the antenna to send and receive
signal in specific frequency bands, in full- or half-duplex, or
modify the radiation pattern so as to not disturb, or at least to
disturb less, closely positioned electronic devices, including
other transponder readers.
[0059] The antenna module 201 communicates with the processor
module 202, to be discussed in detail below, which in turn is in
communication with a data bus module 203 adapted for communication
with other processing means (not shown) as discussed above.
[0060] FIG. 3 discloses a schematic block diagram of an embodiment
according to the invention. In this embodiment, a digital interface
303 is implemented between an antenna module 301 and a processor
module 302 besides to transmission and receiving links, T.sub.x and
R.sub.x respectively. Thus the processor module 302 may instruct
the antenna module to set particular antenna characteristics in
dependence of calculated and detected circumstances. For instance
may the processor module 302 analyse the signal R.sub.x and
conclude that the signal-to-noise ratio would improve if the
antenna characteristics would change to a calculated extent. Thus,
the processor module 302 can send a message according to this
conclusion to the antenna module 301, which will adapt the antenna
characteristics.
[0061] FIG. 4 shows the signal interface between an antenna module
401 and a processor module 402 in greater detail, where a
A/D-converter 403 converts the analogue signal R.sub.x, received by
the antenna module 401, to a digital signal R.sub.xd which is fed
to the processor module 402. A D/A-converter converts a digital
signal T.sub.xd, construed in the processing module 402, into an
analogue signal T.sub.x to be transmitted by the antenna module
401. Thus, the processor module is working in the digital domain
whereas the antenna module, with respect to received and
transmitted signals, work in the analogue domain.
[0062] FIG. 5 shows the processor module in greater detail in a
block diagram according to an embodiment of the invention. The
processor module comprises first and second demodulation blocks 501
and 502, first and second detecting blocks 503 and 504, and first
and second decoding blocks 505 and 506.
[0063] The demodulation modules 501 and 502 each comprises code,
implemented in hardware or software, to implement demodulation
according to different methods or schemes. For demodulation this
may include different filters for down-converting the received
signal R.sub.xd to a baseband. The different blocks may include
different filters, and each block may be designed to deal with
signals from a special transponder signalling in one or two
frequency bands, which may be different for different
transponders.
[0064] Below is table 1, which lists different characteristic for
two different exemplary transponder systems. TABLE-US-00001
Parameter FDX-transponder HDX-transponder Activation frequency
134.2 kHz 134.2 kHz Modulation AM FSK Returned Frequency 129.0 to
133.2 kHz 124.2 kHz (1) 135.2 to 139.4 kHz 134.2 kHz (0) Channel
Coding Modified DBP None Symbol Time 0.23845 ms 0.1288 ms for "1"
0.1192 ms for "0" Bit rate 4194 Hz 7762.5 Hz for "1" 8387.5 Hz for
"0" Number of bits in message 128 112
[0065] The detection modules 503 and 504 each comprises code,
implemented in hardware or software, to implement detection of
symbols according to different methods or schemes. To be further
described in connection with FIGS. 6 and 7. The outcome of
detection is a sequence of bits called a telegram.
[0066] Finally, the decoding modules 505 and 506 each comprises
code, implemented in hardware or software, to implement decoding of
the telegram according to different methods or schemes. The
telegram is analysed and the ID-code is resolved. In FIGS. 8 and 9
are two different telegrams disclosed. The first task in decoding
may for instance be to compare the leading bits of the telegram
with a known preamble. If the leading bits do not match the
preamble the telegram is rejected or considered invalid. Telegrams
according to different transponder systems comprise different
preambles. The integrity of the telegram is checked next for
instance with error detection bits in the telegram. This integrity
test may also differ for different systems.
[0067] Which demodulation, detection and decoding modules to use
may be selected in different ways. For instance may an operator
select the system in which the transponder reader should work which
will determine, for instance by using a database, which modules to
use.
[0068] In a preferred embodiment the processor module 202 comprises
an evaluation and selection module 507. The evaluation and
selection module (ESM) controls the selection of the other modules
and may for instance order a specific set of modules to handle the
reception of a signal. Different characteristics are calculated,
such as signal-to-noise ratio, bit error rate, telegram rejection
rate etc, and saved. This may be performed for a number of
different occasions and the different results compared. The ESM
then selects the combination of modules that will give the best
performance of the reader for further detection of
transponders.
[0069] The ESM may also be adapted to characterise interference in
the environment and possibly adapt and control the antenna
characteristics accordingly or recognise defective transponders and
alarm an operator.
[0070] In one embodiment the ESM uses a number of different
combinations of modules until a combination results in a valid
telegram. This telegram is then forwarded as a valid telegram on
the data bus.
[0071] FIGS. 6 and 7 each disclose in block diagram a different
decoding scheme to be implemented by each detection module 503 and
504, respectively. FIG. 6 disclose a detection method suitable to
use for a half-duplex transponder using two different frequencies
f.sub.0 and f.sub.1 to represent a "0", and a "1", respectively.
FIG. 7 shows a detection method where no signal indicates a "1" and
a signal with frequency f.sub.0 indicates a "0". Both these methods
are known per se and are therefore not further discussed.
[0072] The processor module may comprise several more of each
demodulating, detection and decoding modules all implementing
different methods for performing tasks according to different
transponder reader systems.
[0073] FIG. 10 shows a block diagram of the interface between
antenna means 1001 and processing means 1002 according to the
invention when a full-duplex protocol is used. In this embodiment
the T.sub.x signal is subtracted from the received signal R.sub.x
to form a new modified received signal R.sub.xm. By this operation
the signal R.sub.xm is more easily demodulated and is not so
difficult, that is, do not require as many valid digits, to
resolve.
[0074] It will be obvious that the invention may be varied in a
plurality of ways. Such variations are not to be regarded as a
departure from the scope of the invention. All such modifications
as would be obvious to one skilled in the art are intended to be
included within the scope of the appended claims.
* * * * *